I've recently come across some decryption in the satoshi treasure hunt where I had no idea where to start. As you have said here it is not suitable for more serious codes but I think this will really help with parts of it.

I will come back to this great post to reference it for the next time and have to go to try and solve your code now for practice. This might take a while but it's great to see how many uses you can put excel to. It really is a great tool for anybody to have in their inventory. These posts are always great to learn new skills.